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  1. #include <stdio.h>
  2.  
  3. #define C_LANG    'C'
  4. #define B_LANG    'B'
  5. #define NO_ERROR  0
  6.  
  7. int main(void)
  8. {
  9.    #if C_LANG == 'C' && B_LANG == 'B'
  10.      #undef C_LANG
  11.      #define C_LANG "I know the C language.\n"
  12.      #undef B_LANG
  13.      #define B_LANG "I know BASIC.\n"
  14.      printf("%s%s", C_LANG, B_LANG);
  15.    #elif C_LANG == 'C'
  16.      #undef C_LANG
  17.      #define C_LANG "I only know C language.\n"
  18.      printf("%s", C_LANG);
  19.    #elif B_LANG == 'B'
  20.      #undef B_LANG
  21.      #define B_LANG "I only know BASIC.\n"
  22.      printf("%s", B_LANG);
  23.    #else
  24.      printf("I don't know C or BASIC.\n");
  25.    #endif
  26.  
  27.    return NO_ERROR;
  28. }
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin 
Standard input is empty
compilation info 
prog.c: In function ‘main’:
prog.c:15:10: error: token ""I know the C language.\n"" is not valid in preprocessor expressions
prog.c:19:10: error: token ""I know BASIC.\n"" is not valid in preprocessor expressions
stdout 
Standard output is empty
https://ideone.com/TkzvEk
language:
C (gcc 8.3)
created:
13 years ago
visibility:
public

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